Use of biodegradable hydrocarbon fluids as heat-transfer media

ABSTRACT

The invention relates to the use, as a liquid phase heat-transfer medium, of a fluid having a boiling point in the range of from 200° C. to 400° C. and a boiling range below 80° C., said fluid comprising more than 95% by weight isoparaffins and less than 3% by weight of naphthens, a biocarbon content of at least 95% by weight, containing less than 100 ppm by weight aromatics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a § 371 national stage entry of InternationalApplication No. PCT/EP2017/077456, filed Oct. 26, 2017, which claimspriority to European Application No. 16196115.6, filed Oct. 27, 2016,the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to the use of specific biodegradable fluids asheat-transfer media. The fluids as used in the invention, hereinafterreferred to as being improved fluids, have a narrow boiling range and avery low aromatic content, and exhibit valuable properties making themespecially suited for use as heat-transfer media, incl. as heat-transferfluid and coolant.

BACKGROUND ART

Hydrocarbon fluids find widespread use, including use as heat-transferfluid. Heat-transfer fluids can be used as liquid or liquid/gas fluids,the latter case involving a physical state change.

For example, liquid phase heat-transfer media operate over the broadtemperature range of −115° C. to 400° C., and are designed to be used innon-pressurized systems and low to medium-pressurized systems. A majoradvantage of liquid heat transfer is lower cost installation andoperation. Capital cost is reduced by elimination of large diameterpiping, safety valves, steam traps and water treatment facilities.Operating cost is reduced by low maintenance requirements and reducedmakeup. Liquid/vapor phase heat-transfer fluids also exist. They offer abroad operating temperature range and uniform heat transfer. Other majorbenefits include precise temperature control and low mechanicalmaintenance costs. Also, a heat transfer system that utilizes a vaporphase medium usually requires less fluid than a comparable liquid phasesystem because the equipment fills with vapor instead of liquid.

Hence, there exist a number of different types of heat-transfer fluids,liquid or liquid/vapor, that can be used in non-pressurized orpressurized equipments.

Also, the temperature range of operation is selected according to theend-use. For example end-uses include stationary heat-exchangers,off-road heat-exchangers, with or without primary and secondarycircuits, with or without radiators, pumps, chillers, heaters, coolers,temperature control units, injection units, LBG units, CSP plants, andthe like. Generally, heat-transfer media find application asheat-transfer fluids (i.e. in the industry) and as a coolant (i.e. in acar engine or the like).

Heat-transfer media are also classified according to the temperaturerange. For example, it is widely recognized that the heat transfer mediacan be classified as follows

-   -   Very Low Temperature, −115° C. to 175° C. (e.g. applications in        pharmaceutical manufacturing, environmental test chambers),    -   Low Temperature, −50° C. to 220° C. (e.g. applications in HVAC,        pharmaceutical manufacturing, synthetic fiber manufacturing,        food and beverage, environmental test chambers),    -   Medium Temperature, −30° C. to 315° C. (e.g. applications in oil        and gas processing, chemical industries, plastics processing,        biodiesel manufacturing, natural gas purification),    -   High Temperature, −20° C. to 350° C. (e.g. application in oil        and gas processing, chemical industries, plastics processing,        biodiesel manufacturing, solar energy, gas-to-liquid, plastic        moulding),    -   Ultra High Temperature, −10° C. to 400° C. (e.g. application in        concentrated solar power (CSP), biodiesel production, chemical        industries, gas-to-liquid, refining asphalt).

There exist a great number of players that provide heat transfer media.However, known heat transfer media so far are especially mineral oils,such as alkylated-aromatic fluids.

Companies Nesté Oy and Avantherm have announced their cooperation forthe manufacturing of cooling medium. According to the press release ofApr. 28, 2016, “Neste Renewable Isoalkane to be used for Avantherm'srenewable products for transferring heat and cold”. The product used isthe Neste Renewable Isoalkane which is used thanks to the company'sproprietary NEXBTL technology. However this product is not appropriategiven especially its flash point.

Document WO 2015/044289 discloses a Fischer-Tropsch derived gas oilfraction that can be used in solvent and functional fluid applications.Said document does not disclose a fluid having the defined biocarboncontent. Additionally, said document does not disclose the use of thefluid as a liquid phase heat-transfer medium, such as a heat-transferfluid or a coolant.

Document EP 2 368 967 discloses a solvent composition comprising 5 to30% by weight of C10-C20 normal alkanes and 70 to 95% by weight ofC10-C20 iso-alkanes, produced from raw materials of biological origin.Said document does not disclose the specific use of the fluidspecifically defined in the invention.

There remains a need for a heat-transfer medium that would be frombiologic origin and not fossil, would be biodegradable yet exhibitimproved properties useful for heat-transfer, notably would exhibitappropriate viscosities, heat transfer capacity and the correctoperating range.

SUMMARY OF THE INVENTION

The invention provides the use, as a liquid phase heat-transfer medium,of a fluid having a boiling point in the range of from 200° C. to 400°C. and a boiling range below 80° C., said fluid comprising more than 95%by weight isoparaffins and less than 3% by weight of naphthens, abiocarbon content of at least 95% by weight, containing less than 100ppm by weight aromatics.

As well understood by the skilled person, a boiling range below 80° C.means that the difference between the final boiling point and theinitial boiling point is less than 80° C.

According to one embodiment, the heat-transfer medium is used as aheat-transfer fluid or as a coolant, preferably as a coolant for avehicle engine, more preferably car engine.

According to one embodiment, the heat-transfer medium is used in aclosed-loop system, preferably non-pressurized.

According to one embodiment, the fluid has a boiling point in the rangeof from 220° C. to 340° C., preferably 240° C. to 340° C. and morepreferably 250° C. to 340° C.

According to one embodiment, the boiling range is 240° C.-275° C. or250° C.-295° C. or 285° C.-335° C.

According to one embodiment, the operating temperature range is −50° C.to 260° C., preferably −50° C. to 220° C. Preferably for thisembodiment, the fluid has a boiling range of 240° C.-275° C. or aboiling range of 250° C.-295° C.

According to another embodiment, the operating temperature range is −30°C. to 315° C. Preferably for this embodiment, the fluid has a boilingrange of 285° C.-335° C.

According to one embodiment, the fluid is obtainable by the processcomprising the step of catalytically hydrogenating a feed comprisingmore than 95% by weight of a hydrodeoxygenated isomerized hydrocarbonbiomass feedstock or a feed comprising more than 95% by weight of afeedstock originating from syngas, at a temperature from 80 to 180° C.,at a pressure from 50 to 160 bars, a liquid hourly space velocity of 0.2to 5 hr⁻¹ and a hydrogen treat rate up to 200 Nm³/ton of feed;preferably the feed comprises more than 98%, preferably more than 99% ofa hydrodeoxygenated isomerized hydrocarbon biomass feedstock, and morepreferably consists of a hydrodeoxygenated isomerized hydrocarbonbiomass feedstock, and especially where the biomass is a vegetable oil,an ester thereof or a triglyceride thereof, the feed being morepreferably a hydrotreated vegetable oil (HVO) feed, especially NEXBTL,or wherein the feed comprises more than 98%, preferably more than 99% ofa feedstock originating from syngas, more preferably from renewablesyngas.

According to one variant, in the previous embodiment, a fractionatingstep is carried out before the hydrogenating step, or after thehydrogenating step or both.

According to one embodiment, the fluid contains less than 50 ppm byweight aromatics, and preferably less than 20 ppm by weight.

According to one embodiment, the fluid contains less than 1% by weightof naphthens, preferably less than 500 ppm and advantageously less than50 ppm.

According to one embodiment, the fluid contains less than 5 ppm, evenless than 3 ppm and preferably less than 0.5 ppm sulphur.

According to one embodiment, the fluid has a biodegradability at 28 daysof at least 60%, preferably at least 70%, more preferably at least 75%and advantageously at least 80%, as measured according to the OECD 306standard.

The improved fluids will thus find applications in a number ofapplications, especially those involving a closed loop system,preferably non-pressurized. The fluids may also find applications inpressurized (low to medium) closed loop systems as well as in open loopsystems. The improved fluids may thus be used in a number ofapplications such as pharmaceutical manufacturing, synthetic fibermanufacturing, food and beverage, environmental test chambers,applications in oil and gas processing, chemical industries, plasticsprocessing, biodiesel manufacturing, natural gas purification.

The improved fluids as heat-transfer media find application asheat-transfer fluids (i.e. in the industry) and as a coolant (i.e. in acar engine or the like), the latter being a preferred application of thepresent improved fluids.

In use, the improved fluids of the invention can also comprise anyadditive known in the art.

It is also possible to use mixtures of the improved fluids of theinvention with other fluids, either as the starting heat-transfer mediaor when refilling existing installations. The invention also applies tothe use of the present fluids of the invention for replacing part or allexisting heat-transfer media.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Process for Manufacturing the Improved Fluids Used in the Invention.

The invention makes use of an improved fluid having a boiling point inthe range of from 200 to 400° C. and comprising more than 95%isoparaffins and containing less than 100 ppm aromatics by weight,obtainable by the process comprising the step of catalyticallyhydrogenating a feed comprising more than 95% by weight of ahydrodeoxygenated isomerized hydrocarbon biomass feedstock or a feedcomprising more than 95% by weight of a feedstock originating fromsyngas, at a temperature from 80 to 180° C., at a pressure from 50 to160 bars, a liquid hourly space velocity of 0.2 to 5 hr⁻¹ and anhydrogen treat rate up to 200 Nm³/ton of feed.

According to a first variant, the feed comprises more than 98%,preferably more than 99% of a hydrodeoxygenated isomerized hydrocarbonbiomass feedstock, and more preferably consists of a hydrodeoxygenatedisomerized hydrocarbon biomass feedstock. According to an embodiment,the biomass is a vegetable oil, an ester thereof or a triglyceridethereof. According to an embodiment, the feed is a NEXBTL feed.

According to second variant, the feed comprises more than 98%,preferably more than 99% of a feedstock originating from syngas.According to an embodiment, the feedstock originates from renewablesyngas.

According to an embodiment, the hydrogenation conditions of the processare the following:

-   -   Pressure: 80 to 150 bars, and preferably 90 to 120 bars;    -   Temperature: 120 to 160° C. and preferably 150 to 160° C.;    -   Liquid hourly space velocity (LHSV): 0.4 to 3, and preferably        0.5 to 0.8 hr⁻¹;    -   Hydrogen treat rate be up to 200 Nm³/ton of feed.

According to an embodiment, a fractionating step is carried out beforethe hydrogenating step, or after the hydrogenating step or both;according to an embodiment, the process comprises three hydrogenationstages, preferably in three separate reactors.

The invention thus discloses fluids having a boiling point in the rangeof from 200 to 400° C. and a boiling range below 80° C., said fluidcomprising more than 95% by weight isoparaffins and less than 3% byweight of naphthens, a biodegradability at 28 days of at least 60%, asmeasured according to the OECD 306 standard, a biocarbon content of atleast 95% by weight, containing less than 100 ppm aromatics by weight,and preferably comprising carbon expressed as CH₃ sat less than 30%.

According to an embodiment, the fluid has a boiling point in the range220 to 340° C. and advantageously more than 240° C. and up to 340° C.

The boiling point can be measured according to well-known methods forthe skilled person. As an example, the boiling point can be measuredaccording to ASTM D86 standard.

According to an embodiment, the fluid has a boiling range below 80° C.,preferably below 60° C., more preferably between 35 and 50° C. andadvantageously between 40 and 50° C.

According to an embodiment, the fluid contains less than 50 ppmaromatics, and preferably less than 20 ppm by weight.

According to an embodiment, the fluid contains less than 1% by weight ofnaphthens, preferably less than 500 ppm and advantageously less than 50ppm.

According to an embodiment, the fluid contains less than 5 ppm, evenless than 3 ppm and preferably less than 0.5 ppm sulphur.

According to an embodiment, the fluid comprises more than 98% by weightisoparaffins.

According to an embodiment, the fluid comprises less than 5% by weightof n-paraffins, preferably less than 3% by weight of n-paraffins.

According to an embodiment, the fluid has a ratio of iso-paraffins ton-paraffins of at least 20:1.

According to an embodiment, the fluid comprises more than 95% by weightof molecules with from 14 to 18 carbon atoms as isoparaffins, preferablycomprises by weight, from 60 to 95%, more preferably 80 to 98%, ofisoparaffins selected from the group consisting of C15 isoparaffins, C16isoparaffins, C17 isoparaffins, C18 isoparaffins and mixtures of two ormore thereof.

According to an embodiment, the fluid comprises:

-   -   C15 isoparaffins and C16 isoparaffins in a combined amount of 80        to 98%; or    -   C16 isoparaffins, C17 isoparaffins and C18 isoparaffins in a        combined amount of 80 to 98%; or    -   C17 isoparaffins and C18 isoparaffins in a combined amount of 80        to 98%.

According to an embodiment, the fluid exhibits one or more, preferablyall of the following features:

-   -   the fluid comprises carbon expressed as Cquat less than 3%,        preferably less than 1% and more preferably about 0%;    -   the fluid comprises carbon expressed as CH sat less than 20%,        preferably less than 18% and more preferably less than 15%;    -   the fluid comprises carbon expressed as CH₂ sat more than 40%,        preferably more than 50% and more preferably more than 60%;    -   the fluid comprises carbon expressed as CH₃ sat less than 30%,        preferably less than 28% and more preferably less than 25%;    -   the fluid comprises carbon expressed as CH₃ long chain less than        20%, preferably less than 18% and more preferably less than 15%;    -   the fluid comprises carbon expressed as CH₃ short chain less        than 15%, preferably less than 10% and more preferably less than        9%.

The amount of isoparaffins, naphthens and/or aromatics can be determinedaccording to any known methods for the skilled person. Among thosemethods, mention may be made of gas chromatography.

According to an embodiment, the fluid has a biodegradability at 28 daysof at least 60%, preferably at least 70%, more preferably at least 75%and advantageously at least 80%, as measured according to the OECD 306standard.

According to an embodiment, the fluid has a biocarbon content of atleast 95% by weight, preferably at least 97%, more preferably at least98%, and even more preferably about 100%.

The feedstock will first be disclosed, then the hydrogenation step andthe associated fractionating step, and finally the improved fluids.

Feedstock.

The feedstock or simply feed may, according to a first variant, be afeed which is the result of a process of hydrodeoxygenation followed byisomerization, hereafter “HDO/ISO”, as practiced on a biomass.

This HDO/ISO process is applied on biological raw materials, thebiomass, selected from the group consisting of vegetable oils, animalfats, fish oils, and mixtures thereof, preferably vegetable oils.Suitable vegetable raw materials include rapeseed oil, canola oil, colzaoil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil,linenseed oil, mustard oil, palm oil, arachis oil, castor oil, coconutoil, animal fats such as suet, tallow, blubber, recycled alimentaryfats, starting materials produced by genetic engineering, and biologicalstarting materials produced by microbes such as algae and bacteria.Condensation products, esters, or other derivatives obtained frombiological raw materials may also be used as starting materials, as wellas recycled oils such as Used Fired Methyl Ester Oils (UFOME). Anespecially preferred vegetable raw material is an ester or triglyceridederivative. This material is submitted to an hydrodeoxygenation (HDO)step for decomposing the structure of the biological ester ortriglyceride constituent, and for removing oxygen, phosphorus and sulfur(part of) compounds, concurrently hydrogenating the olefinic bonds,followed by isomerization of the product thus obtained, thus branchingthe hydrocarbon chain and improving the low temperature properties ofthe thus-obtained feedstock.

In the HDO step, hydrogen gas and the biological constituent are passedto the HDO catalyst bed either in countercurrent or concurrent manner.In the HDO step, the pressure and the temperature range typicallybetween 20 and 150 bar, and between 200 and 500° C., respectively. Inthe HDO step, known hydrodeoxygenation catalysts may be used. Prior tothe HDO step, the biological raw material may optionally be subjected toprehydrogenation under milder conditions to avoid side reactions of thedouble bonds. After the HDO step, the product is passed to theisomerization step where hydrogen gas and the biological constituent tobe hydrogenated, and optionally a n-paraffin mixture, are passed to theisomerization catalyst bed either in concurrent or countercurrentmanner. In the isomerization step, the pressure and the temperaturerange between typically 20 and 150 bar, and between 200 and 500° C.,respectively. In the isomerization step, isomerization catalysts knownas such may be typically used.

Secondary process steps can also be present (such as intermediatepooling, scavenging traps, and the like).

The product issued from the HDO/ISO steps may for instance befractionated to give the desired fractions.

Various HDO/ISO processes are disclosed in the literature. WO2014/033762discloses a process which comprises a pre-hydrogenation step, ahydrodeoxygenation step (HDO) and an isomerization step which operatesusing the countercurrent flow principle. EP1728844 describes a processfor the production of hydrocarbon components from mixtures of avegetable or animal origin. The process comprises a pretreatment step ofthe mixture of a vegetable origin for removing contaminants, such as,for example, alkaline metal salts, followed by a hydrodeoxygenation(HDO) step and an isomerization step. EP2084245 describes a process forthe production of a hydrocarbon mixture that can be used as diesel fuelor diesel component by the hydrodeoxygenation of a mixture of abiological origin containing fatty acid esters possibly with aliquots offree fatty acids, such as for example vegetable oils such as sunfloweroil, rape oil, canola oil, palm oil, or fatty oils contained in the pulpof pine trees (tall oil), followed by hydroisomerization on specificcatalysts. EP2368967 discloses such a process and the thus-obtainedproduct.

Company Nesté Oy has developed specific HDO/ISO processes, and iscurrently marketing products thus obtained, under the tradename NexBTL●(diesel, aviation fuel, naphtha, isoalkane). This NexBT● is anappropriate feed for use in the present invention. The NEXBTL feed isfurther described at at the neste oy website.

The feedstock or simply feed may, according a second variant, be a feedwhich is the result of a process of conversion of syngas intohydrocarbons suitable for further processing as a feedstock. Syngastypically comprises hydrogen and carbon monoxide and possibly minorother components, like carbon dioxide. A preferred syngas used in theinvention is renewable syngas, i.e. syngas from renewable sources (incl.renewable energy sources as detailed below).

Representative of possible syngas-based feedstocks are the Gas toliquids (GTL) feedstock, the Biomass to liquids (BTL) feedstock, therenewable Methanol to liquid (MTL) feedstock, renewable steam reforming,and waste-to-energy gasification, as well as more recent methods usingrenewable energy (solar energy, wind energy) to convert carbon dioxideand hydrogen into syngas. An example of this later process is the audi●e-diesel feedstock process. The term syngas also extends to any sourceof material that can be used in a Fischer Tropsch process, such asmethane-rich gases (which may use syngas as intermediate).

The syngas to liquids (STL) process is a refinery process that convertsgaseous hydrocarbons into longer-chain hydrocarbons such as gasoline ordiesel fuel. Renewable methane-rich gases are converted into liquidsynthetic fuels either via direct conversion or via syngas as anintermediate, for example using the Fischer Tropsch process, Methanol toGasoline process (MTG) or Syngas to gasoline plus process (STG+). Forthe Fischer Tropsch process, the effluents produced are Fischer-Tropschderived.

By “Fischer-Tropsch derived” is meant that a hydrocarbon composition is,or derives from, a synthesis product of a Fischer-Tropsch condensationprocess. The Fischer-Tropsch reaction converts carbon monoxide andhydrogen (syngas) into longer chain, usually paraffinic hydrocarbons.The overall reaction equation is straightforward (but hides mechanisticcomplexity):n(CO+2H₂)═(—CH₂—)n+nH₂O+heat,in the presence of an appropriate catalyst and typically at elevatedtemperatures (e.g., 125 to 300° C., preferably 175 to 250° C.). and/orpressures (e.g., 5 to 100 bars, preferably 12 to 50 bars). Hydrogen:carbon monoxide ratios other than 2:1 may be employed if desired. Thecarbon monoxide and hydrogen may themselves be derived from organic orinorganic, natural or synthetic sources, typically either from naturalgas or from organically derived methane. For examples it can also bederived from biomass or from coal.

The collected hydrocarbon composition containing a continuousiso-paraffinic series as described above may preferably be obtained byhydroisomerisation of a paraffinic wax, preferably followed by dewaxing,such as solvent or catalytic dewaxing. The paraffinic wax is preferablya Fischer-Tropsch derived wax.

Hydrocarbon cuts may be obtained directly from the Fischer-Tropschreaction, or indirectly for instance by fractionation of Fischer-Tropschsynthesis products or preferably from hydrotreated Fischer-Tropschsynthesis products.

Hydrotreatment preferably involves hydrocracking to adjust the boilingrange (see, e.g., GB-B-2077289 and EP-A-0147873) and/orhydroisomerisation, which can improve cold flow properties by increasingthe proportion of branched paraffins. EP-A-0583836 describes a two-stephydrotreatment process in which a Fischer-Tropsch synthesis product isfirstly subjected to hydroconversion under conditions such that itundergoes substantially no isomerisation or hydrocracking (thishydrogenates the olefinic and oxygen-containing components), and then atleast part of the resultant product is hydroconverted under conditionssuch that hydrocracking and isomerisation occur to yield a substantiallyparaffinic hydrocarbon fuel. It is possible to adjust the isomerizationprocess so as to obtain mainly isoparaffins with the required carbondistribution. The syngas-based feedstock is isoparaffinic in nature asit contains more than 90% isoparaffins.

Other post-synthesis treatments, such as polymerisation, alkylation,distillation, cracking-decarboxylation, isomerisation andhydroreforming, may be employed to modify the properties ofFischer-Tropsch condensation products, as described for instance in U.S.Pat. Nos. 4,125,566 and 4,478,955. Examples of Fischer-Tropsch processeswhich for example can be used to prepare the above-describedFischer-Tropsch derived collected hydrocarbon composition are theso-called commercial Slurry Phase Distillate technology of Sasol, theShell Middle Distillate Synthesis Process and the “AGC-21” Exxon Mobilprocess. These and other processes are for example described in moredetails in EP-A-776959, EP-A-668342, U.S. Pat. Nos. 4,943,672,5,059,299, WO-A-9934917 and WO-A-9920720.

The desired fraction(s) may subsequently be isolated for instance bydistillation.

Feedstocks typically contain less than 15 ppm of sulphur, preferablyless than 8 ppm and more preferably less than 5 ppm, especially lessthan 1 ppm, as measured according to EN ISO 20846. Typically thefeedstocks will comprise no sulphur as being biosourced products.

Before entering the hydrogenation unit, a pre-fractionation step cantake place. Having a more narrow boiling range entering the unit allowshaving a more narrow boiling range at the outlet. Indeed typical boilingranges of pre-fractionated cuts are 220 to 330° C. while cuts without apre-fractionating step typically have a boiling range from 150° C. to360° C.

Hydrogenation Step.

The feedstock issued from HDO/ISO or from syngas is then hydrogenated.The feedstock can optionally be pre-fractionated.

Hydrogen that is used in the hydrogenation unit is typically a highpurity hydrogen, e.g. with a purity of more than 99%, albeit othergrades can be used.

Hydrogenation takes place in one or more reactors. The reactor cancomprise one or more catalytic beds. Catalytic beds are usually fixedbeds.

Hydrogenation takes place using a catalyst. Typical hydrogenationcatalysts include but are not limited to: nickel, platinum, palladium,rhenium, rhodium, nickel tungstate, nickel molybdenum, molybdenum,cobalt molybdenate, nickel molybdenate on silica and/or alumina carriersor zeolites. A preferred catalyst is Ni-based and is supported on analumina carrier, having a specific surface area varying between 100 and200 m²/g of catalyst.

The hydrogenation conditions are typically the following:

-   -   Pressure: 50 to 160 bars, preferably 80 to 150 bars, and most        preferably 90 to 120 bars or 100 to 150 bars;    -   Temperature: 80 to 180° C., preferably 120 to 160° C. and most        preferably 150 to 160° C.;    -   Liquid hourly space velocity (LHSV): 0.2 to 5 hr⁻¹, preferably        0.4 to 3, and most preferably 0.5 to 0.8;    -   Hydrogen treat rate: adapted to the above conditions, which can        be up to 200 Nm³/ton of feed.

The temperature in the reactors can be typically about 150-160° C. andthe pressure can be typically about 100 bars while the liquid hourlyspace velocity can be typically about 0.6 h⁻¹ and the treat rate isadapted, depending on the feed quality and the first process parameters.

The hydrogenation process of the invention can be carried out in severalstages. There can be two or three stages, preferably three stages,preferably in three separate reactors. The first stage will operate thesulphur trapping, hydrogenation of substantially all unsaturatedcompounds, and up to about 90% of hydrogenation of aromatics. The flowexiting from the first reactor contains substantially no sulphur. In thesecond stage the hydrogenation of the aromatics continues, and up to 99%of aromatics are hydrogenated. The third stage is a finishing stage,allowing an aromatic content as low as 100 ppm by weight or even lesssuch as below 50 ppm, more preferably less than 20 ppm, even for highboiling products.

The catalysts can be present in varying or substantially equal amountsin each reactor, e.g. for three reactors according to weight amounts of0.05-0.5/0.10-0.70/0.25-0.85, preferably 0.07-0.25/0.15-0.35/0.4-0.78and most preferably 0.10-0.20/0.20-0.32/0.48-0.70.

It is also possible to have one or two hydrogenation reactors instead ofthree.

It is also possible that the first reactor be made of twin reactorsoperated alternatively in a swing mode. This may be useful for catalystcharging and discharging: since the first reactor comprises the catalystthat is poisoned first (substantially all the sulphur is trapped inand/or on the catalyst) it should be changed often.

One reactor can be used, in which two, three or more catalytic beds areinstalled.

It may be necessary to insert quenches on the recycle to cool effluentsbetween the reactors or catalytic beds to control reaction temperaturesand consequently hydrothermal equilibrium of the hydrogenation reaction.In a preferred embodiment, there is no such intermediate cooling orquenching.

In case the process makes use of 2 or 3 reactors, the first reactor willact as a sulphur trap. This first reactor will thus trap substantiallyall the sulphur. The catalyst will thus be saturated very quickly andmay be renewed from time to time. When regeneration or rejuvenation isnot possible for such saturated catalyst the first reactor is consideredas a sacrificial reactor which size and catalyst content both depend onthe catalyst renewal frequency.

In an embodiment the resulting product and/or separated gas is/are atleast partly recycled to the inlet of the hydrogenation stages. Thisdilution helps, if this were to be needed, maintaining the exothermicityof the reaction within controlled limits, especially at the first stage.Recycling also allows heat-exchange before the reaction and also abetter control of the temperature.

The stream exiting the hydrogenation unit contains the hydrogenatedproduct and hydrogen. Flash separators are used to separate effluentsinto gas, mainly remaining hydrogen, and liquids, mainly hydrogenatedhydrocarbons. The process can be carried out using three flashseparators, one of high pressure, one of medium pressure, and one of lowpressure, very close to atmospheric pressure.

The hydrogen gas that is collected on top of the flash separators can berecycled to the inlet of the hydrogenation unit or at different levelsin the hydrogenation units between the reactors.

Because the final separated product is at about atmospheric pressure, itis possible to feed directly the fractionation stage, which ispreferably carried out under vacuum pressure that is at about between 10to 50 mbars, preferably about 30 mbars.

The fractionation stage can be operated such that various hydrocarbonfluids can be withdrawn simultaneously from the fractionation column,and the boiling range of which can be predetermined.

Therefore, fractionation can take place before hydrogenation, afterhydrogenation, or both.

The hydrogenation reactors, the separators and the fractionation unitcan thus be connected directly, without having to use intermediatetanks. By adapting the feed, especially the initial and final boilingpoints of the feed, it is possible to produce directly, withoutintermediate storage tanks, the final products with the desired initialand final boiling points. Moreover, this integration of hydrogenationand fractionation allows an optimized thermal integration with reducednumber of equipment and energy savings.

Fluids Used in the Invention.

The fluids used in the invention, hereafter referred to simply as “theimproved fluids” possess outstanding properties, in terms of anilinepoint or solvency power, molecular weight, vapour pressure, viscosity,defined evaporation conditions for systems where drying is important,and defined surface tension.

The improved fluids are primarily isoparaffinic and contain more than95% by weight isoparaffins, preferably more than 98% by weight.

The improved fluids typically contain less than 1% by weight ofnaphthens, preferably less than 500 ppm and advantageously less than 50ppm.

Typically, the improved fluids comprise carbon atoms number from 6 to30, preferably 8 to 24 and most preferably from 9 to 20 carbon atoms.The fluids especially comprise a majority, i.e. more than 90% by weight,of molecules with from 14 to 18 carbon atoms as isoparaffins. Preferredimproved fluids are those comprising by weight, from 60 to 95%,preferably 80 to 98%, of isoparaffins selected from the group consistingof C15 isoparaffins, C16 isoparaffins, C17 isoparaffins, C18isoparaffins and mixtures of two or more thereof.

Preferred improved fluids comprise:

-   -   C15 isoparaffins and C16 isoparaffins in a combined amount of 80        to 98%; or    -   C16 isoparaffins, C17 isoparaffins and C18 isoparaffins in a        combined amount of 80 to 98%; or    -   C17 isoparaffins and C18 isoparaffins in a combined amount of 80        to 98%.

Examples of preferred improved fluids are those comprising:

-   -   from 30 to 70% of C15 isoparaffins and from 30 to 70% C16        isoparaffins, preferably from 40 to 60% of 015 isoparaffins and        from 35 to 55% C16 isoparaffins;    -   from 5 to 25% of C15 isoparaffins, from 30 to 70% C16        isoparaffins and from 10 to 40% of C17 isoparaffins, preferably        from 8 to 15% of 015 isoparaffins, from 40 to 60% C16        isoparaffins and from 15 to 25% of C17 isoparaffins;    -   from 5 to 30% of C17 isoparaffins and from 70 to 95% 018        isoparaffins, preferably from 10 to 25% of C17 isoparaffins and        from 70 to 90% C18 isoparaffins.

The improved fluids exhibit a specific branching distribution.

Branching rates of isoparaffins as well as carbon distribution isdetermined using the NMR method (as well as GC-MS) and determination ofeach type of carbon (with no hydrogen, with one, two or threehydrogens). C quat sat represents the saturated quaternary carbon, CHsat represents the saturated carbon with one hydrogen, CH₂ satrepresents the saturated carbon with two hydrogens, CH₃ sat representsthe saturated carbon with three hydrogens, CH₃ long chain and CH₃ shortchain represent the CH₃ group on a long chain and a short chain,respectively where the short chain is one methyl group only and a longchain is a chain having at least two carbons. The sum of CH₃ long chainand CH₃ short chain is CH₃ sat.

The improved fluids typically comprise carbon expressed as Cquat lessthan 3%, preferably less than 1% and more preferably about 0%.

The improved fluids typically comprise carbon expressed as CH sat lessthan 20%, preferably less than 18% and more preferably less than 15%.

The improved fluids typically comprise carbon expressed as CH₂ sat morethan 40%, preferably more than 50% and more preferably more than 60%.

The improved fluids typically comprise carbon expressed as CH₃ sat lessthan 30%, preferably less than 28% and more preferably less than 25%.

The improved fluids typically comprise carbon expressed as CH₃ longchain less than 20%, preferably less than 18% and more preferably lessthan 15%.

The improved fluids typically comprise carbon expressed as CH₃ shortchain less than 15%, preferably less than 10% and more preferably lessthan 9%.

The improved fluids have a boiling point in the range of from 200 to400° C. and also exhibit an enhanced safety, due to the very lowaromatics content.

The improved fluids typically contain less than 100 ppm, more preferablyless than 50 ppm, advantageously less than 20 ppm aromatics (measuredusing a UV method). This is especially useful for high temperatureboiling products, typically products having a boiling point in the range300-400° C., preferably 320-380° C.

The boiling range of the improved fluids is preferably not more than 80°C., preferably not more than 70° C., more preferably not more than 60°C., even more preferably between 35 and 50° C. and advantageouslybetween 40 and 50° C.

The improved fluids also have an extremely low sulphur content,typically less than 5 ppm, even less than 3 ppm and preferably less than0.5 ppm, at a level too low to be detected by the usual low-sulphuranalyzers.

The Initial Boiling Point (IBP) to Final Boiling Point (FBP) range isselected according to the particular use and composition. An InitialBoiling Point of more than 250° C. allows classification as free of VOC(Volatile Organic Compounds) according to the directive 2004/42/CE.

Biodegradation of an organic chemical refers to the reduction incomplexity of the chemical through metabolic activity of microorganisms.Under aerobic conditions, microorganisms convert organic substances intocarbon dioxide, water and biomass. OECD 306 method, is available forassessing biodegradability of individual substances in seawater. OECDMethod 306 can be carried out as either a shake flask or Closed Bottlemethod and the only microorganisms added are those microorganisms in thetest seawater to which the test substance is added. In order to assessthe biotic degradation in seawater, a biodegradability test wasperformed which allows the biodegradability to be measured in seawater.The biodegradability was determined in the Closed Bottle test performedaccording to the OECD 306 Test Guidelines. The biodegradability of theimproved fluids is measured according to the OECD Method 306.

The OECD Method 306 is the following:

The closed bottle method consists on dissolution of a pre-determinedamount of the test substance in the test medium in a concentration ofusually 2-10 mg/1, with one or more concentrations being optionallyused. The solution is kept in a filled closed bottle in the dark in aconstant temperature bath or enclosure controlled within a range of15-20° C. The degradation is followed by oxygen analyses over a 28-dayperiod. Twenty-four bottles are used (8 for test substance, 8 forreference compound and 8 for sweater plus nutriment). All analyses areperformed on duplicate bottles. Four determinations of dissolved oxygen,at least, are performed (day 0, 5, 15 and 28) using a chemical orelectrochemical method.

Results are thus expressed in % degradability at 28 days. The improvedfluids have a biodegradability at 28 days of at least 60%, as measuredaccording to the OECD 306 standard, preferably at least 70% by weight,more preferably at least 75% and advantageously at least 80%.

The invention uses the products of natural origin like startingproducts. The carbon of a biomaterial comes from the photosynthesis ofthe plants and thus of atmospheric CO₂. The degradation (by degradation,one will understand also combustion/incineration at the end of thelifetime) of these CO2 materials thus does not contribute to the warmingsince there is no increase in the carbon emitted in the atmosphere. Theassessment CO₂ of the biomaterials is thus definitely better andcontributes to reduce the print carbon of the products obtained (onlyenergy for manufacture is to be taken into account). On the contrary, afossil material of origin being also degraded out of CO₂ will contributeto the increase in the CO₂ rate and thus to climate warming. Theimproved fluids according to the invention will thus have a print carbonwhich will be better than that of compounds obtained starting from afossil source.

The invention thus improves also the ecological assessment during themanufacture of the improved fluids. The term of “bio-carbon” indicatesthat carbon is of natural origin and comes from a biomaterial, asindicated hereafter. The content of biocarbon and the content ofbiomaterial are expressions indicating the same value.

A renewable material of origin or biomaterial is an organic material inwhich carbon comes from CO₂ fixed recently (on a human scale) byphotosynthesis starting from the atmosphere. On ground, this CO₂ iscollected or fixed by the plants. At sea, CO₂ is collected or fixed bymicroscopic bacteria or plants or algae carrying out a photosynthesis. Abiomaterial (carbon natural origin 100%) presents an isotopic ratio¹⁴C/¹²C higher than 10⁻¹², typically about 1.2×10⁻¹², while a fossilmaterial has a null ratio. Indeed, the isotope ¹⁴C is formed in theatmosphere and is then integrated by photosynthesis, according to ascale of time of a few tens of years at the maximum. The half-life of¹⁴C is 5730 years. Thus the materials resulting from photosynthesis,namely the plants in a general way, have necessarily a maximum contentof isotope ¹⁴C.

The determination of the content of biomaterial or content of biocarbonis given pursuant to standards ASTM D 6866-12, method B (ASTM D 6866-06)and ASTM D 7026 (ASTM D 7026-04). Standard ASTM D 6866 concerns“Determining the Biobased Content of Natural Range Materials UsingRadiocarbon and Isotope Ratio Mass Spectrometry Analysis”, whilestandard ASTM D 7026 concerns “Sampling and Reporting of Results forDetermination of Biobased Content of Materials via Carbon IsotopeAnalysis”. The second standard mentions the first in its firstparagraph.

The first standard describes a test of measurement of the ratio mC/¹²Cof a sample and compares it with the ratio ¹⁴C/¹²C of a sample renewablereference of origin 100%, to give a relative percentage of C of originrenewable in the sample. The standard is based on the same concepts thatthe dating with ¹⁴C, but without making application of the equations ofdating. The ratio thus calculated is indicated as the “pMC” (percentModem Carbon). If the material to be analyzed is a mixture ofbiomaterial and fossil material (without radioactive isotope), then thevalue of pMC obtained is directly correlated with the quantity ofbiomaterial present in the sample. The value of reference used for thedating to ¹⁴C is a value dating from the years 1950. This year wasselected because of the existence of nuclear tests in the atmospherewhich introduced great quantities of isotopes into the atmosphere afterthis date. The reference 1950 corresponds to a value pMC of 100. Takinginto account the thermonuclear tests, the current value to be retainedis approximately 107.5 (what corresponds to a factor of correction of0.93). The signature into radioactive carbon of a current plant is thusof 107.5. A signature of 54 pMC and 99 pMC thus correspond to a quantityof biomaterial in the sample of 50% and 93%, respectively.

The compounds according to the invention come at least partly frombiomaterial and thus present a content of biomaterial from at least 95%.This content is advantageously even higher, in particular more than 98%,more preferably more than 99% and advantageously about 100%. Thecompounds according to the invention can thus be bio-carbon of 100%biosourced or on the contrary to result from a mixture with a fossilorigin. According to an embodiment, the isotopic ratio ¹⁴C/¹²C isbetween 1.15 and 1.2×10⁻¹².

According to an embodiment, the fluid has a flash point higher than 100°C., preferably higher than 105° C., preferentially higher than 110° C.,more preferentially higher than 115° C.

All percentages and ppm are by weight unless indicated to the contrary.Singular and plural are used interchangeably to designate the fluid(s).

The following example illustrates the invention without limiting it.

EXAMPLE

A feedstock being a NEXBTL feedstock (isoalkane) is used in the processof the invention. The following conditions for hydrogenation are used:

The temperature in the reactors is about 150-160° C.; the pressure isabout 100 bars and the liquid hourly space velocity is 0.6 h⁻¹; thetreat rate is adapted. The catalyst used is nickel on alumina.

Fractionating is carried out to provide 3 fluids to be used in theinvention.

The resulting products have been obtained, with the followingproperties.

The following standards have been used to determine the followingproperties:

Flash point EN ISO 2719 Pour point EN ISO 3016 Density at 15° C. EN ISO1185 Viscosity at 40° C. EN ISO 3104 Aniline point EN ISO 2977 Thermalconductivity¹ Internal Flash method Specific heat² Method by calorimetry

1. A specific apparatus is used, comprising two tubes of aluminium, oneinner and one outer. The fluid to be measured is placed in the annularspace between the two tubes. An energy pulse (dirac type) is applied onthe inner tube and the temperature is measured on the outer tube,whereby a thermogram is obtained.

Knowing the thermal diffusivity, density and specific heat of two layersof the two tubes of aluminium as a function of temperature, and knowingthe density and specific heat of the fluid to be analysed, one candeduce the thermal conductivity of the fluid as a function oftemperature.

Calibration of the Apparatus.

The apparatus is first calibrated with a reference sample, SERIOLA 1510(heat transfer medium) at different temperatures. The different thermalproperties were measured separately before.

Sample Preparation.

The sample is mixed and introduced (using syringe) into the annularspace between the two tubes. The loaded apparatus is then placed in achamber regulated in temperature.

Measurement Protocol.

For each temperature measurement, the following procedure is followed.The sample is stabilized at a given temperature. Then light flashes areapplied on the inner face of the inner tube and the rise in temperatureof the outer face of the outer tube is recorded over time.

Based on average values obtained with at least 3 measures at each giventemperature, the thermal conductivity is calculated.

2. The specific heat is measured using a DSC calorimeter (DSC NETZSCH204 Phoenix), which is compliant with standards ISO 113587, ASTM E1269,ASTM E968, ASTM E793, ASTM D3895, ASTM D3417, ASTM D3418, DIN 51004, DIN51007 and DIN 53765.

Characteristic Ex. 1 Ex. 2 Ex. 3 Aromatic content (ppm) <20 <20 <20Sulfur content (ppm) 0.1 0.1 0.11 % isoparaffins (w/w) 98.9 95.1 96.2 %n-paraffins (w/w) 1.1 4.9 3.8 % naphthenic (w/w) 0 0 0 C15 (iso) 48.3511.45 0 C16 (iso) 42.80 47.89 1.58 C17 (iso) 2.52 18.57 14.17 C18 (iso)0.38 17.07 79.69 C quat sat 0 0 0 CH sat 12.1 10.9 10.2 CH₂ sat 64.967.8 70.7 CH₃ sat 22.9 21.2 19.1 CH₃ long chain 14.2 13.3 12 CH₃ shortchain 8.7 8 7.1 Biocarbon content (%) 97 97 98 Initial Boiling Point (°C.) 247.0 259.5 293.6 5% point (° C.) 255.7 270.2 296.7 50% point (° C.)258.9 274.5 298.5 95% point (° C.) 266.8 286.4 305.3 Dry point (° C.)269.0 287.5 324.1 OECD biodegradability 80 83 83 (28 days) (%) Flashpoint (° C.) 115 125 149.5 Density at 15° C. (kg/m3) 776.4 780.3 787.2Viscosity at 40° C. (mm²/s) 2.495 2.944 3.870 Pour point (° C.) −81 −60−45 Aniline point (° C.) 93.2 95.7 99.5 Thermal conductivity Lambda 28/0.130  27/0.135  23/0.138 (at ° C. in W/(m · K))  73/0.125  73/0.128 88/0.137  128/0.124  127/0.126  158/0.127 Specific heat 30.3/215431.3/2202 31.3/2185 (at ° C. in J/(kg · K)) 74.8/2336 74.8/232489.7/2377 129.2/2540  129.2/2503  158.9/2695 

The three fluids also are colorless, odorless, have a purity accordingto the European Pharmacopoeia suitable for food grade application, andare solvent class A according to CEN/TS 16766.

These results show that the improved fluids described in the inventionare especially useful for use as heat transfer media.

The thermal conductivity values are indicative of a conductivity that issuperior to the one of standard mineral oils, at the same viscosity (byup to 7%), the heat transfer rate is improved. The specific heat issuperior to the one of standard mineral oils (by up to 11%).

The results also show that it is possible to obtain heat transfer mediahaving kinematic viscosity higher than 3, especially from 3 to 6 mm²/s,good heat capacity and a wide temperature range of operation.

The fluids of the invention will thus find applications in a number ofapplications, especially those involving a closed loop system,preferably non-pressurized. The fluids may also find applications inpressurized (low to medium) closed loop systems as well in open loopsystems.

The thermal stability has been evaluated in the present invention bymeasuring, according to the GB/T 23800-2009 standard, the percentage ofdecomposition of the fluid. The test performed in the present examplediffers from the standard by the temperature and the duration of thetest. According to the example, the percentage of decomposition of thefluid has been measured after 500 hours at 320° C.

The fluid of Ex. 3 according to the invention and defined above has beencompared with other commercial fluids: an alkylbenzene fluid, adibenzyltoluene isomer, a mineral base oil and a hydrotreated mineralbase oil.

Thermal stability results are given in table 2 below.

TABLE 2 thermal stability results Hydrotreated Dibenzyltoluene Mineralbase mineral base Ex. 3 Alkylbenzene isomer oil oil Thermal 1.6 9.9 6.926 5.8 stability (% of decomposition)

The fluid defined in the present invention has a much better thermalstability than comparative fluids of the prior art, with less than 2% ofdecomposition after 500 hours at 320° C.

The invention claimed is:
 1. Method for transferring heat, said methodcomprising: introducing a liquid fluid into a closed loop system, thefluid having an initial boiling point and a final boiling point in therange of from 200° C. to 400° C. and a boiling range below 80° C., saidfluid comprising more than 95% by weight of isoparaffins, less than 3%by weight of naphthenes, a biocarbon content of at least 95% by weight,and less than 100 ppm by weight aromatics; and transferring heat by thefluid in a car engine, wherein the step of transferring heat comprises astep of cooling the car engine, wherein the boiling range of the fluidis 240° C.-275° C. or 250° C.-295° C. or 285° C.-335° C. wherein thefluid has a flash point higher than 115° C.
 2. Method of claim 1,wherein the step of transferring heat is performed at a temperatureranging from −50° C. to 260° C.
 3. Method of claim 2, wherein the fluidin the step of transferring heat has a boiling range of 240° C.-275° C.or a boiling range of 250° C.-295° C.
 4. Method of claim 1, wherein thestep of transferring heat is performed at a temperature ranging from−30° C. to 315° C.
 5. Method of claim 4, wherein the fluid in the stepof transferring heat has a boiling range of 285° C.-335° C.
 6. Method ofclaim 1, wherein the fluid contains less than 50 ppm aromatics. 7.Method of claim 1, wherein the fluid contains less than 1% by weight ofnaphthenes.
 8. Method of claim 1, wherein the fluid further containsless than 5 ppm sulphur.
 9. Method of claim 1, wherein the fluid has abiodegradability at 28 days of at least 60%, as measured according tothe OECD 306 standard.
 10. Method of claim 1, wherein the fluid containsless than 20 ppm by weight of aromatics and less than 500 ppm by weightof naphthenes and wherein the fluid has an initial boiling point and afinal boiling point in the range of from 240° C. to 340° C.
 11. Methodof claim 1, wherein the closed-loop system is a non-pressurizedclosed-loop system.
 12. The method of claim 1, wherein the fluid furthercomprises less than 4% by weight of n-paraffins.
 13. Method fortransferring heat, said method comprising: introducing a liquid fluidinto a dosed-loop system, the fluid having an initial boiling point anda final boiling point in the range of from 200° C. to 400° C. and aboiling range below 80° C., said fluid comprising at least 95.1% byweight of isoparaffins, less than 3% by weight of naphthenes, abiocarbon content of at least 95% by weight, and less than 50 ppm byweight aromatics, transferring heat by the fluid in a car engine,wherein the step of transferring heat comprises a step of cooling thecar engine, wherein the step of transferring heat is operated at atemperature ranging from −50° C. to 260° C. and wherein the fluid has aboiling range of 240° C.-275° C. or a boiling range of 250° C.-295° C.wherein the fluid has a flash point higher than 115° C.
 14. The methodof claim 13, wherein the fluid further comprises less than 4% by weightof n-paraffins.
 15. Method for transferring heat, said methodcomprising: introducing a liquid fluid into a closed-loop system, thefluid haying an initial boiling point and a final boiling point in therange of from 200° C. to 400° C. and a boiling range below 80° C. saidfluid comprising at least 95.1% by weight of isoparaffins, less than 1%by weight of naphthenes, a biocarbon content of at least 95% by weight,and less than 50 ppm by weight aromatics, transferring heat by the fluidin a car engine, wherein the step of transferring heat comprises a stepof cooling the car engine, wherein the step of transferring heat isoperated at a temperature ranging from −30° C. to 315° C. and whereinthe fluid has a boiling range of 285° C.-335° C. wherein the fluid has aflash point higher than 115° C.
 16. The method of claim 15, wherein thefluid further comprises less than 4% by weight of n-paraffins.